1. Field of the Invention
The present invention relates to a process for producing friction plates having a flat friction surface that are used as, for example, friction plates for lock-up clutches of torque converters, and a system for producing the same.
2. Description of the Related Art
The lock-up clutch of a torque converter is controlled so as to be in an ON state in its coupling region to directly connect a pump impeller to a turbine impeller, thereby eliminating any slip between the two impellers and thus improving the transmission efficiency. Such a lock-up clutch is known as disclosed in, for example, Japanese Patent Application Laid-open No. 5-71610. The ON state of the lock-up clutch is established as follows: the inner chamber of a lock-up clutch chamber is connected to a hydraulic oil supply side and the outer chamber is connected to a low pressure side, thereby increasing the pressure of the inner chamber relative to the pressure of the outer chamber; and the resulting pressure difference presses the friction plate towards the inner wall of a side cover, thereby frictionally engaging the friction lining with the inner wall.
In this case, the annular friction lining of the friction plate has a flat friction surface without oil groove, unlike the clutch friction plate having an oil groove on its friction surface that is used in a wet type multiple plate clutch for a normal transmission system. It is therefore possible to prevent the hydraulic pressure of the inner chamber from leaking into the outer chamber through a gap between the friction lining and the side cover, whereby a good clutch ON state can be maintained.
Conventionally, the entire annular friction lining having a flat friction surface is formed as a single lining having no seams is punched out of friction lining tape material. However, the production of such friction linings generates a large amount of lining material scrap, leading to a very poor yield which is a large barrier to reducing the cost of friction plates.
The present invention has been carried out in view of the above-mentioned circumstances, and it is an object of the present invention to provide a process for producing friction plates having a flat friction surface with low cost by forming an annular friction lining from lining segments that are punched out of friction lining tape material with good yield. Furthermore, it is another object of the present invention to provide a system for producing such friction plates.
In order to achieve the above-mentioned objects, in accordance with a first characteristic of the present invention, there is proposed a process for producing a friction plate having a flat friction surface by adhering an annular friction lining having a flat friction surface to a side of a core plate. The process comprises steps of provisionally arranging a plurality of sector-shaped lining segments, punched out of a friction lining tape material, in a generally annular form on an index table so as not to overlap with each other; correcting the provisional arrangement of the lining segments into an annular form having no gaps between the lining segments by moving together the plurality of lining segments, provisionally arranged on the index table, towards the centre of the index table, and adhering the plurality of lining segments, correctly arranged in the annular form, to the side of the core plate.
In accordance with the above-mentioned arrangement, the plurality of sector-shaped lining segments can be punched out of the friction lining tape material with good yield; by forming an annular friction lining having a flat friction surface from these lining segments and adhering the lining to the side of the core plate, a friction plate having a flat friction surface can be produced efficiently, thereby contributing to a reduction in the cost of the friction plate.
Furthermore, in accordance with a second characteristic of the present invention, in addition to the above-mentioned first characteristic, there is proposed a process for producing a friction plate having a flat friction surface wherein in the step of provisionally arranging the plurality of lining segments on the index table each of the lining segments punched out of the friction lining tape material is placed in turn on the index table that is rotating.
In accordance with the above-mentioned arrangement, the plurality of lining segments can be provisionally arranged on the index table with good efficiency.
Furthermore, in accordance with a third characteristic of the present invention, in addition to the above-mentioned first characteristic, there is proposed a process for producing a friction plate having a flat friction surface further comprising steps of transferring the group of lining segments correctly arranged on the index table from the index table to the side of the core plate that has been coated with an adhesive and carrying out provisional adhesion, and actually adhering the group of provisionally adhered lining segments to the core plate by compressing/heating.
In accordance with the above-mentioned arrangement, the arrangement of the group of lining segments can be checked before actual adhesion to re-correct the arrangement thus contributing to an improvement in quality.
Furthermore, in accordance with a fourth characteristic of the present invention, there is proposed a system for producing a friction plate having a flat friction surface by adhering an annular friction lining having a flat friction surface to a side of a core plate, comprising a lining segment provisional arrangement station in which a plurality of sector-shaped lining segments, punched out of a friction lining tape material, are provisionally arranged in a generally annular form on an index table so as not to overlap with each other; a lining segment arrangement correction station in which the provisional arrangement of the lining segments is corrected into an annular form having no gaps between the lining segments by moving together the plurality of lining segments, provisionally arranged on the index table, towards the centre of the index table by means of a plurality of arrangement correction members provided along the outer peripheries of the lining segments, the group of correctly arranged lining segments being retained by the arrangement correction members; a lining segment provisional adhesion station in which the group of lining segments retained by the arrangement correction members is placed on a side of the core plate that has been coated with an adhesive, thereby carrying out provisional adhesion; and a lining segment actual adhesion station in which the group of provisionally adhered lining segments is pressed against the core plate by a compressing/heating plate.
In accordance with the above-mentioned arrangement, the plurality of sector-shaped lining segments can be obtained from the friction lining tape material with good yield and a friction plate having a flat friction surface can be produced efficiently using these segments, thereby contributing to a reduction in the cost of the friction plate.
Furthermore, in accordance with a fifth characteristic of the present invention, in addition to the above-mentioned fourth characteristic, there is proposed a system for producing a friction plate having a flat friction surface wherein the index table of the lining segment provisional arrangement station has a large number of vacuum holes for retaining by vacuum pressure the provisionally arranged lining segments.
In accordance with the above-mentioned arrangement, the lining segments can be provisionally arranged on the index table reliably, and it is possible to prevent each of the lining segments from displacing.
Furthermore, in accordance with a sixth characteristic of the present invention, in addition to the above-mentioned fourth characteristic, there is proposed a system for producing a friction plate having a flat friction surface wherein the arrangement correction members of the lining segment arrangement correction station have a large number of vacuum holes for retaining by vacuum pressure the group of correctly arranged lining segments.
In accordance with the above-mentioned arrangement, the group of correctly arranged lining segments can be retained by the arrangement correction members easily and reliably and it is thus possible to prevent each of the lining segments from displacing.
Furthermore, in accordance with a seventh characteristic of the present invention, in addition to the above-mentioned fourth characteristic, there is proposed a system for producing a friction plate having a flat friction surface wherein the lining segment arrangement correction station includes a cam mechanism for synchronously sliding the plurality of arrangement correction members in a radial direction.
In accordance with the above-mentioned arrangement, the plurality of arrangement correction members can be moved together, and arrangement of all the lining segments can be corrected rapidly.